Ultrafast electron transfer at the ZIS1−x/UCN S-scheme interface enables efficient H2O2 photosynthesis coupled with tetracycline degradation

Coupling H₂O₂ production with organic pollutant degradation can effectively overcome the sluggish kinetics of water oxidation while concurrently addressing environmental pollution challenges. In this work, an S-defect-rich ZnIn₂S₄/g-C₃N₄ (ZIS_1−x/UCN) S-scheme heterojunction photocatalyst was constructed by in situ growing ZIS_1−x nanosheets on porous ultrathin UCN. The designed ZIS_1−x/UCN photocatalyst demonstrates enhanced visible light absorption, abundant active sites, and intimate interfacial contact. The optimized ZIS_1−x/UCN-1.0 photocatalyst exhibits outstanding dual functionality, simultaneously achieving an H₂O₂ production rate of 2902.2 μmol g⁻¹ h⁻¹ and 91.3 % tetracycline (50 mg L⁻¹) degradation efficiency. This H₂O₂ performance represents a 1.63-fold enhancement compared to its activity in pure water (1777.0 μmol g⁻¹ h⁻¹). Through comprehensive characterization including femtosecond transient absorption spectroscopy (fs-TAS), in situ irradiation X-ray photoelectron spectroscopy (ISI-XPS), and in situ X-ray absorption fine structure spectroscopy (XAFS), we unequivocally confirm the S-scheme charge transfer mechanism. This S-scheme induced unique electronic structure not only fosters ultrafast electron transfer at the interface (3.54 ps) but also significantly enhances the redox capacity of photogenerated carriers. Collectively, this work opens new avenues for the dual application of photocatalytic technology in both energy production and environmental remediation.